Can you re-Anodize something that already Anodized ?

heavyp

You heard it here first
So I just got myself a new project bike an Iron Horse Sunday, first things to be done is get it stripped and resprayed/powdercoated but the linkage rockers are already anodized.

Can you re-anodize something thats already been done or how do you go about stripping the old anodize thats already on there ?

Any info would be sweet, cheers.
 

SummitFever

Eats Squid
Are you re-anodizing it yourself? If not, whoever you get to do the anodizing will have a prep solution that will strip the old anodizing off (something caustic soda based).

Anodizing will not change the surface texture of the item. I mention this because if the linkages are dull, matt or scratched and you want a high gloss type finish, you will need to remove the existing ano and then polish etc. before anodizing. DIY ano removal will involve caustic soda from some source (eg. oven cleaner). I haven't personally done this. For ano removal I just sandblast but you do end up with a matt finish which is great for painting, but needs polishing before re-anodizing.
 

heavyp

You heard it here first
Thanks so much for the info, No i was going to take it to someone. Its the linkages for my Iron Horse Sunday and I didn't want to risk losing material off them as bearings need to be put back into them one there done.
 

redbruce

Eats Squid
Thanks so much for the info, No i was going to take it to someone. Its the linkages for my Iron Horse Sunday and I didn't want to risk losing material off them as bearings need to be put back into them one there done.
Make sure you explain that (need to maintain bearing housing dimensions) to them.

Anodizing is a chemical reaction with the aluminium (as opposed to an independent surface coating like paint) and in removing it is actually removing aluminium as well.

A competent metal finisher and all should be OK.
 
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slippy

Likes Bikes and Dirt
Have successfully removed anodizing at home with oven cleaner. It was a lot of work and not worth the effort.
 

fatboyonabike

Captain oblivious
why don't you leave the old bearings in place, then hit them with the sand blaster..once done, pop out old bearings and discard - the bearing recess will still be good to go, as the old ones would have protected it from the abrasive sand!
 

komdotkom

Likes Bikes and Dirt
Thread revival.
I've got a frame coming from another RB member which is clear anodised but has some minor scuffs, cable rub and scratches on it. I like bikes to look good, any ideas on what are my options to repair the clear anodising on it?
 

Miguel76

Likes Bikes
Apologies for jumping in your thread, I’ll take my request elsewhere if necessary; does anyone know an anodiser who would do 3 knobs from my shock? In black?
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
Thread revival.
I've got a frame coming from another RB member which is clear anodised but has some minor scuffs, cable rub and scratches on it. I like bikes to look good, any ideas on what are my options to repair the clear anodising on it?
Is it clear-coated (painted) or anodised? Chemically stripping anodising removes the hardened oxide layer from the aluminum, which make the material thinner. Given bike frames can be quite thin to begin with this could be a precarious option. Could the scuffed/damaged areas just be polished out?

Apologies for jumping in your thread, I’ll take my request elsewhere if necessary; does anyone know an anodiser who would do 3 knobs from my shock? In black?
Generally most places that do anodising can do colour anodising, but the problem with what you're asking is (I'm guessing) you don't know the material of the shock knobs. It's all well and good to say it's (aluminium) alloy, but which one? Anodisers will use different chemical processes depending on the specific material - ie: parts made from 2024 won't go in the same tanks as 6061 due to the different composition. It's also not particularly cheap.

Probably ~10 years ago I had a 120mm x 120mm x 6mm plate I'd milled into a (camera) filter holder anodised black. I had to wait several weeks until they were putting through a batch of the same material and it still cost me around $50 (back then!).
 

Miguel76

Likes Bikes
Thanks for the info Beeb. The previous owner polished the anodising off, back to bare alloy and I’d like it black again… maybe I’ll try the sharpie:)
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
Thanks for the info Beeb. The previous owner polished the anodising off, back to bare alloy and I’d like it black again… maybe I’ll try the sharpie:)
Tends to rub off or turn dark purple over time, but hey - it's cheap and easy to re-apply! :)
 

komdotkom

Likes Bikes and Dirt
I use Collins Adonic in Blackburn Victoria for our race car stuff, and they'll do small parts when they are running that colour but you will have to wait. We get a lot of stuff 'hard anodsised', the finish isn't quite ad good but more scratch resistant. I got a set of rotor hats done a few weeks ago for $120.

Is it clear-coated (painted) or anodised? Chemically stripping anodising removes the hardened oxide layer from the aluminum, which make the material thinner. Given bike frames can be quite thin to begin with this could be a precarious option. Could the scuffed/damaged areas just be polished out?
Not sure, frame hasn't arrived yet but I'm assuming it's clear anodised. The problem with polishing is that you set out to polish one part, the next thing you know you've been on the polisher all day and the frame is like a mirror but it oxidises really quickly.
I might just paint it.
 
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